Disease:Cartilaginous and fibrous free bodies are often present in the knee joint. They are of various origins: they may originate from the cartilage of the joint surface or from the menisci; furthermore they may arise as a consequence of the cartilage-producing disease of the synovium.

Symptom: They may migrate within the joint and get pinched between the bones, which may result in lightening-like pain and joint lock.

Treatment: The cartilage fragments can be surgically removed by arthroscopy (with the use of a fiberscope). If the weight-bearing cartilage surface is damaged, mosaic arthroplasty can be performed, which consists of the transplantation of intact cartilaginous islands from surfaces not involved in weight-bearing to the diseased/injured areas.